Bearing mechanism, spindle motor and data storage medium drive apparatus

Abstract

A bearing mechanism includes a shaft, a bearing portion, and a cover closing a bottom end of the bearing portion. The bearing portion and the cover are preferably connected to one another by laser welding. A surface of a welded portion formed by the laser welding includes an inclined surface which is inclined such that the further from a central axis a portion thereof is, the axially higher the portion is. With this unique structure, contamination of lubricant used inside the bearing mechanism by fumes generated due to the laser welding is minimized, and therefore a reliable and durable bearing mechanism is provided.

1. A bearing mechanism comprising:
 a shaft; 
 a bearing portion retaining a lubricant in a space between the shaft and the bearing portion, the bearing portion rotatably supporting the shaft concentrically about a central axis of the shaft; and 
 a cover arranged to cover an end portion of a lower portion of the bearing portion in an axial direction; wherein 
 the bearing portion includes a lower inner circumferential surface arranged opposite from an outer circumferential surface of the cover, and a bottom end surface extending continuously from the lower inner circumferential surface and in a radially outward direction; 
 a fitted portion is arranged between the bottom end surface of the bearing portion and the cover and includes a welded portion defined by a plurality of beads; 
 an inclined surface is provided at a surface of the welded portion such that the further from the central axis a portion of the inclined surface is, the axially higher the portion of the inclined surface is; and 
 the bearing portion includes a notched portion extending from a radially outward location to a radially inward location at a same axial height as the cover. 
 
     
     
       2. The bearing mechanism according to  claim 1 , wherein the inclined surface includes a substantially convex shape when viewed perpendicularly to the central axis. 
     
     
       3. The bearing mechanism according to  claim 1 , wherein a portion of the bead of the welded portion makes contact with an outer circumferential edge of the bearing portion. 
     
     
       4. The bearing mechanism according to  claim 1 , wherein the bottom end surface is arranged axially above a bottom surface of the cover. 
     
     
       5. The bearing mechanism according to  claim 1 , wherein a radial width of the bottom end surface is smaller than a distance between a substantially central portion of the bead and an edge of the bead. 
     
     
       6. The bearing mechanism according to  claim 1 , wherein the substantially central portion of the bead is arranged above the bottom end surface. 
     
     
       7. The bearing mechanism according to  claim 1 , wherein the bearing portion includes a housing and a sleeve. 
     
     
       8. A spindle motor comprising:
 the bearing mechanism according to  claim 1 ; 
 a rotor magnet concentric with the shaft; and 
 a stator arranged radially opposite to the rotor magnet. 
 
     
     
       9. A data storage medium drive comprising:
 a data storage medium; 
 the spindle motor according to  claim 8 ; and 
 a case accommodating therein a head moving mechanism arranged to store and retrieve data with respect to the data storage medium. 
 
     
     
       10. A bearing mechanism comprising:
 a shaft; 
 a bearing portion retaining a lubricant in a space between the shaft and the bearing portion, the bearing portion rotatably supporting the shaft concentrically about a central axis of the shaft; and 
 a cover arranged to cover an end portion of a lower portion of the bearing portion in an axial direction; wherein 
 the bearing portion includes a lower inner circumferential surface arranged opposite from an outer circumferential surface of the cover, and a bottom end surface extending continuously from the lower inner circumferential surface and in a radially outward direction; 
 a fitted portion is arranged between the bottom end surface of the bearing portion and the cover and includes a welded portion defined by a plurality of beads; 
 an inclined surface is provided at a surface of the welded portion such that the further from the central axis a portion of the inclined surface is, the axially higher the portion of the inclined surface is; and 
 a portion of the plurality of beads of the welded portion makes contact with an outermost circumferential edge of the bearing portion. 
 
     
     
       11. The bearing mechanism according to  claim 10 , wherein the bearing portion includes a notched portion extending from a radially outward location to a radially inward location at a same axial height as the cover portion. 
     
     
       12. The bearing mechanism according to  claim 10 , wherein the inclined surface includes a substantially convex shape when viewed perpendicularly to the central axis. 
     
     
       13. The bearing mechanism according to  claim 10 , wherein a portion of the bead of the welded portion makes contact with an outer circumferential edge of the bearing portion. 
     
     
       14. The bearing mechanism according to  claim 10 , wherein the bottom end surface is arranged axially above a bottom surface of the cover. 
     
     
       15. The bearing mechanism according to  claim 10 , wherein a radial width of the bottom end surface is smaller than a distance between a substantially central portion of the bead and an edge of the bead. 
     
     
       16. The bearing mechanism according to  claim 10 , wherein the substantially central portion of the bead is arranged above the bottom end surface. 
     
     
       17. The bearing mechanism according to  claim 10 , wherein the bearing portion includes a housing and a sleeve. 
     
     
       18. A spindle motor comprising:
 the bearing mechanism according to  claim 10 ; 
 a rotor magnet concentric with the shaft; and 
 a stator arranged radially opposite to the rotor magnet. 
 
     
     
       19. A data storage medium drive comprising:
 a data storage medium; 
 the spindle motor according to  claim 18 ; and 
 a case accommodating therein a head moving mechanism arranged to store and retrieve data with respect to the data storage medium.